How to tell the direction on a cloudy night?

In the dark, you can tell the direction by the compass. Compass, called Sina in ancient times, is mainly composed of magnetic needles installed on the shaft. Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangential direction of magnetic meridian. The south pole of the magnetic needle points to the geographical south pole (magnetic north pole), and you can use this property to identify the direction.

It is often used in navigation, geodesy, tourism and military affairs. The invention of the compass with physical direction indication has three parts, namely Sina, compass and magnetic needle, all of which belong to the invention of China. According to ancient mine records, it first appeared in the Cishan area during the Warring States Period.

Compass is the result of China ancient working people's understanding of magnet magnetism in long-term practice. As one of four great inventions of ancient china, its invention has played an inestimable role in the development of human science, technology and civilization. In ancient China, the compass was first used for rituals, etiquette, military affairs and divination, and to determine the orientation when looking at Feng Shui.